Learn more about COVID-19 in Saskatchewan:

Google Translate Disclaimer

A number of pages on the Government of Saskatchewan's website have been professionally translated in French. These translations are identified by a yellow box in the right or left rail that resembles the link below. The home page for French-language content on this site can be found at:

Renseignements en Français

Where an official translation is not available, Google™ Translate can be used. Google™ Translate is a free online language translation service that can translate text and web pages into different languages. Translations are made available to increase access to Government of Saskatchewan content for populations whose first language is not English.

Software-based translations do not approach the fluency of a native speaker or possess the skill of a professional translator. The translation should not be considered exact, and may include incorrect or offensive language. The Government of Saskatchewan does not warrant the accuracy, reliability or timeliness of any information translated by this system. Some files or items cannot be translated, including graphs, photos and other file formats such as portable document formats (PDFs).

Any person or entities that rely on information obtained from the system does so at his or her own risk. Government of Saskatchewan is not responsible for any damage or issues that may possibly result from using translated website content. If you have any questions about Google™ Translate, please visit: Google™ Translate FAQs.

Understanding Crop Rotation and Crop Diseases

By: Barbara Ziesman, AAg, Provincial Specialist, Plant Disease

Crop rotation has an important role in an integrated approach to disease management. Diverse crop rotations can be used to break disease cycles, and reduce pathogen levels and disease pressure between host crops. When the pathogen survives in the field (either in the soil or on infected residue), time away from a host crop will provide time for the infected residue to decompose and for the number of living pathogen spores or resting structures in the soil to decline. This means that there will be lower levels of the pathogen present to cause disease the next time a susceptible crop is grown.

Crop rotation as a disease management tool will have the most significant impact when:

  • The disease has a narrow host range. This means there are more options to select non-host crops to add to the crop rotation to provide time for pathogen levels to reduce. For example, crop rotation is a very effective management strategy for diseases like blackleg, clubroot, ascochyta blight and aphanomyces root rot, as these diseases only infect a small number major crops in Saskatchewan. On the other hand, crop rotation will be less effective for sclerotinia diseases, as the pathogen has the ability to cause disease in more than 400 plant types, including most of the broad-leafed crops grown in Saskatchewan.
  • The pathogen overwinters in the field (in the soil or on infected residue) and spore dispersal only occurs over short distances. When the pathogen overwinters in the field, strategies such as crop rotation can directly impact the amount of pathogen present to cause disease. However, when the pathogen is primarily introduced through other means, crop rotation may have less of an impact. An example of this is stripe rust of cereals. The stripe rust pathogen does not typically overwinter in Canada, and the pathogen is often introduced to a field via spores carried on wind currents. Since the spores are introduced through an external source, crop rotation within a specific field will not impact disease levels in a given year.

The length of crop rotation needed will depend on how the pathogen survives in the field and the half-life of the spores or overwintering structures of the pathogen. As a general rule of thumb, a four-year crop rotation is recommended. However, a three-year crop rotation can be very effective for some diseases (e.g.: Fusarium head blight or clubroot), and a longer crop rotation is needed for others (e.g.: aphanomyces root rot of pea and lentil, where an eight-year rotation is recommended).

The chart below* illustrates some of the major and economically important diseases of Saskatchewan crops and the major crop types that they can infect. This can be used to identify crop rotations to provide adequate disease breaks to reduce pathogen levels and disease pressure.

Crop Rotation Table
a Caused by a complex of pathogens including Fusarium¸ Rhizoctonia and Pythium species. These organisms can cause disease in a broad number of host crops.
b This includes all cereal leaf spots. Some leaf spot pathogens only cause disease in specific cereal crops.
c Ascochyta blight in field pea, lentil and chickpea are caused by different ascochyta species. *Darker colour indicates that the disease is often considered economically important. A light colour indicates that the disease may not always be economically important due to a combination of host genetics, plant architecture or other factors that influence disease development.

We need your feedback to improve saskatchewan.ca. Help us improve